Design Patterns in Java

A design pattern is a predefined solution to a common software problem.

If you’ve ever gone to a tailor, he may have asked you a series of questions based on your needs. Those questions are part of a pattern used to identify your design pattern. If you observe how your mother cooks, you will notice some patterns for various types of foods. So there are some design patterns in software implementations. These are the things you should be aware of before becoming a software engineer.

Design patterns and elements of reusable object-oriented software is the title of the book. Gang of Four is the title of a book written by four authors. According to them, design patterns can be classified into three types. Creational — various methods of producing objects Relationships between these objects are structural.

Interaction or communication between these objects is referred to as behavioral interaction.

By the way, these design patterns do not represent all of the patterns in software development. There are numerous unofficial and undocumented patterns that may be useful in specific situations. These 23 design patterns, on the other hand, are classics that every software engineer should be aware of. Design patterns have the advantage of allowing us to communicate with other developers on a more abstract level.

You could say to a coworker, “Hey, we can use the factory pattern to improve this code.” Simply use the pattern’s name to convey the concept.

Advantages

• You don’t need to write a lot of code to express that idea.
• You will learn how to write reusable, extensible, and maintainable software.
• Regardless of the programming language you use or the type of application you develop.
• The advantage of studying and comprehending these design patterns is that it improves your design skills.
• Finally, understanding design patterns can help you learn and apply new frameworks and libraries faster.

Before diving into these design patterns, I recommend that you first learn object-oriented programming concepts in Java. Because the majority of these design patterns are built around reusable and expendable objects. As a result, you should understand OOP concepts like inheritance, polymorphism, abstraction, encapsulation, coupling, and cohesion.

Patterns of Creational Design

These design patterns rely heavily on class instantiation. They are dealing with object creational mechanisms that attempt to create objects that are situationally appropriate. In Java, we all know that the new keyword is used to create new objects. It can, however, cause design issues or add complexity to the design. This issue is addressed by creational design patterns, which control the creation of objects.

• The singleton property ensures that an object only has one instance.
• The factory method generates objects without specifying which class they are.
• Objects can be created using the Abstract Factory without specifying their concrete type.
• A prototype is a new object created from an existing one.
• Builder is a program used to create complex objects.

Structural Design Pattern

The composition of classes and objects is central to these design patterns. Structured design patterns, in other words, reduce complexity by identifying relationships.

• Adapter — a class that wraps an interface around an existing class to allow two incompatible classes to work together.
• Bridge — a decoupled abstraction that allows two classes to vary independently of one another
• A composite object is one that combines several objects into a single object.
• Flyweight — reduces the cost of complex object models.
• Proxy — assists in lowering the cost of complex object models.
• Facade — a straightforward interface to a more complex underlying object.
• Decorator — allows an object’s behavior to be dynamically extended at run time.

Behavioral Design Patterns

Class object communication is the focus of these design patterns. In other words, object interaction follows a pattern. These patterns are used to recognize and implement our requirements.

• Using Chain of Responsibility, delegate commands to a chain of processing objects.
• Command:- creates objects with actions and parameters.
• An interpreter is someone who speaks a specific language.
• Iterator :- accesses the elements of an object in a sequential manner without revealing its underlying representation.
• Mediator: Because it is the only class with detailed knowledge of its methods, it allows for loose coupling between classes.
• Memento: the ability to restore an object to its original state. The observer pattern is a publish/subscribe pattern that allows multiple observers to see the same event.
• When an object’s internal state changes, its behavior can change.
• The strategy enables the run-time selection of an algorithm from a family. The Template Method defines the skeleton of an algorithm as an abstract class, allowing subclasses to extend it.
• By combining the hierarchy of methods into a single object, the Visitor decouples an algorithm from an object structure.